Mechanical disconnects for parallel power lanes in hybrid electric propulsion systems

ABSTRACT

A hybrid propulsion system includes a heat engine configured to drive a heat engine shaft. An electric motor is configured to drive a motor shaft. A transmission system includes at least one gear box. The transmission system is configured to receive rotational input power from each of the heat engine shaft and the motor shaft and to convert the rotation input power to output power. The motor shaft includes a disconnect mechanism to allow the heat engine to rotate with the electric motor stopped. The heat engine shaft includes a disconnect mechanism to allow the electric motor to rotate with the heat engine stopped.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Ser. No. 62/820,064 filed Mar. 18, 2019 and U.S. Provisional Patent Application Ser. No. 62/812,474 filed Mar. 1, 2019, the disclosures of each are herein incorporated by reference in their entirety

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to aircraft engines, and more particularly to hybrid aircraft engines.

2. Description of Related Art

Aircraft engines vary in efficiency and function over a plurality of parameters, such as thrust requirements, air temperature, air speed, altitude, and the like. Aircraft require the most thrust at take-off, wherein the demand for engine power is the heaviest. However, during the remainder of the mission, the aircraft engines often do not require as much thrust as during take-off. The size and weight of the engines allows them to produce the power needed for take-off, however after take-off the engines are in effect over-sized for the relatively low power required to produce thrust for cruising in level flight.

The conventional techniques have been considered satisfactory for their intended purpose. However, there is an ever present need for improved aircraft engines. This disclosure provides a solution for this need.

SUMMARY OF THE INVENTION

A hybrid propulsion system includes a heat engine configured to drive a heat engine shaft. An electric motor is configured to drive a motor shaft. A transmission system includes at least one gear box. The transmission system is configured to receive rotational input power from each of the heat engine shaft and the motor shaft and to convert the rotation input power to output power. The motor shaft includes a disconnect mechanism to allow the heat engine to rotate with the electric motor stopped. The heat engine shaft includes a disconnect mechanism to allow the electric motor to rotate with the heat engine stopped.

The at least one gearbox can include a combining gear box connecting to the heat engine shaft and to the motor shaft to combine rotational input power from the heat engine and electric motor for providing rotational output power to an output shaft. The at least one gearbox can also include a turbine gear box. The turbine gear box can be connected between the heat engine shaft and a shaft for driving a turbine and a compressor to drive the turbine and compressor at a different rotational speed from the heat engine. The disconnect mechanism of the motor shaft can be located between the combining gear box and the electric motor. The disconnect mechanism of the heat engine shaft can be located between the combining gear box and the heat engine.

The heat engine shaft and motor shaft can be concentric. The at least one gear box can include a reduction gear box connected to each of the heat engine shaft and the motor shaft. The heat engine shaft can connect to a turbine shaft for driving a turbine and compressor. The disconnect mechanism of the motor shaft can be located between the electric motor and the reduction gear box. The disconnect mechanism of the heat engine shaft can be located between the heat engine and the electric motor. The heat engine shaft can run through the motor shaft and through the disconnect mechanism of the motor shaft. It is also contemplated that the heat engine shaft and the motor shaft can be combined as a single common shaft connected to the transmission system.

These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:

FIG. 1 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a first gearbox arrangement;

FIG. 2 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a second gearbox arrangement;

FIG. 3 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a third gearbox arrangement;

FIG. 4 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a fourth gearbox arrangement;

FIG. 5 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a fifth gearbox arrangement;

FIG. 6 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a sixth gearbox arrangement;

FIG. 7 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a seventh gearbox arrangement;

FIG. 8 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing an eighth gearbox arrangement;

FIG. 9 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a ninth gearbox arrangement;

FIG. 10 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a tenth gearbox arrangement;

FIG. 11 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing an eleventh gearbox arrangement;

FIG. 12 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a twelfth gearbox arrangement;

FIG. 13 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a thirteenth gearbox arrangement;

FIG. 14 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a fourteenth gearbox arrangement;

FIG. 15 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a fifteenth gearbox arrangement;

FIG. 16 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a first gear box arrangement; and

FIG. 17 is a schematic view of an exemplary embodiment of a hybrid propulsion system constructed in accordance with the present disclosure, showing a second gear box arrangement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of a hybrid propulsion system in accordance with the disclosure is shown in FIG. 1 and is designated generally by reference character 100. Other embodiments of hybrid propulsion systems in accordance with the disclosure, or aspects thereof, are provided in FIGS. 2-17, as will be described. The systems and methods described herein can be used to provide hybrid propulsion, e.g., for improving fuel efficiency in aircraft.

The hybrid propulsion system 100 includes a heat engine (or motor) 102 configured to drive a heat engine shaft 104. An electric motor 106 is configured to drive an electric motor shaft 108. A transmission system 110 includes at least one gearbox. The transmission system 110 is configured to receive rotational input power from each of the heat engine shaft 104 and the motor shaft 108 and to convert the rotation input power to output power, as indicated by the circular arrow in FIG. 1.

The at least one gearbox includes a combining gearbox 112 connecting to the heat engine shaft 104 and to the motor shaft 108 to combine rotational input power from the heat engine 102 and electric motor 106 for providing rotational output power to an output shaft 114, which can drive a reduction gearbox 116 for turning an aircraft propeller, fan, or any other suitable type of air mover for example. A turbine gearbox 118 is included, which is connected between the heat engine shaft 104 and a shaft 120 for driving a turbine 122 and a compressor 124 to drive the turbine 122 and compressor 124 at a different rotational speed from the heat engine 102. For example, through the turbine gearbox 118, the heat engine 102 can run at 8000 revolutions per minute (RPM), the heat engines exhaust can be recovered by the turbine 122 to drive the compressor 120 at 35,000 RPM. The turbine gearbox 118 can be a two speed transmission or constant velocity transmission (CVT) which can eliminate the need for a variable inlet guide vane (VIGV) controlling the compressor 124. It is also contemplated that the turbine 122 and compressor 124 can separately connect to the turbine gear box 118, e.g., using a concentric shaft for the compressor such as the shaft 1246 shown in FIG. 14, so that the turbine 122 and compressor 124 can rotate at different rotational speeds. These types of turbine gearbox can apply to each of the turbine gearboxes described below, even if not specifically repeated.

Those skilled in the art will readily appreciate that while described herein in the context of driving the turbine 122 and compressor 124, that the turbine 122 can actually add power to the shaft 120 and therefore cooperates with the heat engine 102 to drive the combining gearbox 112, however, in configurations herein where the turbine 122 and compressor 124 spin at a common speed the compressor 124 and turbine 122 are collectively referred to herein as driven.

The compressor 120 compresses air and supplies the compressed air to the heat engine 102 through the air line 126, which includes heat exchanger 128 for cooling the compressed air.

After combustion in the heat engine 102, the combustion products are supplied through a combustion products line 130 to the turbine 122, which extracts power from the compressed combustion products before exhausting them. The configurations shown in FIGS. 2-15 also include similar air lines 126, heat exchangers 128, and combustion products lines 130, and the details for such are not repeated below for each Figure. Also, unless specified otherwise, the configurations in each of FIGS. 2-15 include an output shaft 114 connecting between a combining gearbox (e.g. combining gearbox 112) and reduction gearbox 116, the details of which will not be repeated below for each Figure. The electric motor 106 can be powered to boost horse power, e.g., for take-off, in parallel with the heat motor 102, and can be powered down, e.g., for cruising in level flight, where only the heat motor 102 is needed for power. It is also contemplated that the electric motor 106 can be used as a generator to recharge the battery, e.g. source 1138 of FIG. 13, when power is available from the heat engine 102 or form wind milling the propeller to drive the reduction gear box 116. The compressor 124 and turbine 122 improve the thermal efficiency of the heat engine 102. Similar benefits are derived with the configurations described below with respect to FIGS. 2-15. The dashed line in FIG. 1 schematically indicates that the turbine 122 can optionally be moved to connect directly to the combining gearbox 112, much as described below with respect to FIG. 13, which switch in turbine position can also be applied to other arrangements described below wherein the compressor and turbine are shown and described as being on a common shaft.

With reference now to FIG. 2, a system 200 includes a combining gearbox 212 connecting to the heat engine shaft 204, the motor shaft 208, and a shaft 220 for driving the turbine 222 and compressor 224. The combining gearbox 212 combines rotational input power from the heat engine (or motor) 202 and electric motor 206 for providing rotational output power to an output shaft 114 and to drive the turbine 222 and compressor 224. While connected on a common shaft 220, the turbine 222 and compressor 224 can be connected on opposite sides of the combining gearbox 212 as shown in FIG. 2. It is also contemplated that the turbine 222 and compressor 224 can both be connected on one side of the combining gearbox 212, as shown in FIG. 3. The portion of the combining gearbox 212 that drives the shaft 220 can be a two speed transmission or constant velocity transmission (CVT) which can eliminate the need for a variable inlet guide vane (VIGV) controlling the compressor 224. This applies to arrangements described below wherein the turbine and compressor connect directly to a combined gearbox, even if not specifically repeated.

With reference now to FIG. 4, a system 300 is shown wherein the heat engine shaft 304 and the electric motor shaft 308 are connected for common rotation. A reduction gearbox 316, e.g. for ultimately outputting power to a propeller, is connected to a common output shaft 305 of the electric motor 306 and the heat engine 302. A turbine gearbox 332 is connected between the heat engine shaft 304 and a shaft 320 for rotation of the turbine 322 and compressor 324 at a different rotational speed from the heat engine 302 and electric motor 306. The broken line in FIG. 4 indicates that the position of the heat engine 302 and electric motor 306 can be reversed on the common shaft 305. If there is a requirement to guarantee power from one of the heat engine 302 or electric motor 306 in the event of stoppage of the other, each of the heat engine 302 and electric motor can be connected to the reduction gearbox 316 through a concentric shaft, e.g. as indicated by the broken lines between the electric motor 306 and the reduction gear box 316. The same applies to other configurations herein where the heat engine and electric motor are shown and described as having a common output shaft.

With reference now to FIG. 5, in the system 400, the heat engine shaft 404 and electric motor shaft 408 are concentric with a shaft 420 for rotation of the turbine 422 and compressor 424. The heat engine shaft 404 and electric motor shaft 408 can be a common shaft 405 as shown in FIG. 5, or can themselves be concentric with one another as indicated by the broken lines in FIG. 5. A reduction gearbox 416 is connected to each of the heat engine shaft 404 and the electric motor shaft 408, e.g., for driving a propeller with rotational input from the heat engine 402 and electric motor 406. The reduction gearbox 416 connects to a shaft 420 for rotation of the turbine 422 and compressor 424.

With reference now to FIG. 6, a system 500 has a heat engine shaft 504 and the electric motor shaft 508 connected for common rotation. A combining gearbox 512 connects to the common output shaft 505 of the electric motor 506 and the heat engine 502 and a shaft 520 for driving a turbine 522 and compressor 524, to combine rotational input power from the heat engine 502 and electric motor 506 for providing rotational output power to an output shaft 114 and to drive the turbine 522 and compressor 524. The turbine 522 and compressor 524 are connected on opposite sides of the combining gearbox 512. As shown in FIG. 7, it is also contemplated that the turbine 522 and compressor 524 can both be on one side of the combining gearbox 512. The broken lines in FIGS. 6 and 7 schematically indicate that the positions of the heat motor 502 and electric motor 506 can be switched.

Referring now to FIG. 8, a system 600 includes a combining gearbox 612 connecting to the heat engine shaft 604 and to the electric motor shaft 608 to combine rotational input power from the heat engine 602 and electric motor 606 for providing rotational output power to an output shaft 114. A turbine driver motor/generator 634 is connected to a shaft 620 for driving a turbine 622 and a compressor 624 to drive the turbine 622 and compressor 624 at a different rotational speed ratio from the heat engine 602 and electric motor 606. The compressor 624 can therefore be a variable speed compressor. An electrical system 636 includes a storage 638, e.g., a battery, battery bank, capacitor, capacitor bank, super capacitor or super capacitor bank, flywheel or flywheel bank, or the like, is connected to a first inverter/rectifier component 640 for supplying power from the storage 638 to drive the electric motor 606 or in an energy recovery mode, to store into the storage 638 energy generated by driving the electric motor 606 in a generator mode. The electrical system 636 includes a second invert/rectifier component 642 for supplying power to drive the turbine driver motor 634, or to recover energy into the storage 638 from the turbine drive motor 634 if run in a generator mode. The broken line in FIG. 8 schematically indicates that the position of the motor 634 and compressor can be switched on the shaft 620. FIGS. 9, 10, 11, and 12 each show similar electrical systems 636 and the description thereof is not repeated below.

With reference now to FIG. 9, a system 700 has the heat engine shaft 704 and the electric motor shaft 108 are connected for common rotation. A reduction gearbox 716 connected to a common output shaft 714 of the electric motor 706 and the heat engine 702. A turbine driver motor 734 is connected to a shaft 720 for driving a turbine 722 and a compressor 724 at a different rotational speed from the heat engine 702 and electric motor 706. The broken arrows in FIG. 9 schematically indicate that the position of the heat engine 702 and the electric motor 706 can be switched on the common shaft 714, and that the positions of the motor 734 and compressor 724 can be switched on the shaft 720.

Referring now to FIG. 10, in the system 800 the heat engine shaft 804 and the electric motor shaft 808 are connected for common rotation. A reduction gearbox 816 is connected to a common output shaft 814 of the electric motor 806 and the heat engine 802. A turbine gearbox 818 is connected through a clutch 844 between the heat engine shaft 804 and a shaft 820 for driving a turbine 822 and a compressor 824 at a different rotational speed ratio from the heat engine 802 and electric motor 802 when the clutch 844 is engaged. The shaft 820 for driving the turbine 822 and compressor 824 is connected to a turbine driver motor 834 to drive the turbine 822 and compressor 824 independently from the heat engine 802 and electric motor 806 when the clutch 844 is disengaged. The broken lines in FIG. 10 schematically indicate that the positions of the clutch 844 and the turbine gearbox 818 can be switched. The clutch 844 can prevent electrical losses at steady state because the clutch engages when system 800 steady state operation, e.g., cruising in level flight, so the shaft 820 is connected to the heat engine 802 to avoid electrical conversion losses. In transients, the clutch 844 can open or disconnect to allow the motor 834 to drive the shaft 820 at a different speed ratio from the heat engine 802 as described above.

With respect to FIG. 11, a system 900 includes a heat engine shaft 904 and electric motor shaft 908 that are concentric with the shaft 20 for rotation of the turbine 922 and compressor 924 similar to the arrangement in FIG. 5. A reduction gearbox 916 is connected to each of the heat engine shaft 904 and the electric motor shaft 908, e.g., as a common shaft 905 or concentric with one another as described above with respect to FIG. 5. A clutch 944 in the shaft 920 connects between the heat engine 902 and a turbine driver motor 934 for rotating the turbine 922 and compressor 924 with the reduction gear box 916 when the clutch 944 is engaged, and to drive the turbine 922 and compressor 924 independently from the heat engine 902 and electric motor 906 when the clutch 944 is disengaged.

With reference now to FIG. 12, a system 1000 includes a heat engine shaft 1004 and electric motor shaft 1008 are connected for common rotation. A reduction gearbox 1016 is connected to a common output shaft 1014 of the electric motor 1006 and the heat engine 1002. The upper broken lines in FIG. 12 schematically indicate that the positions of the heat engine 1002 and the motor 1006 can be switched on the shaft 1014. A clutch 1044 connects between the reduction gearbox 1016 and a turbine driver motor 1034 connected to a shaft 1020 for driving a turbine 1022 and a compressor 1024 with rotational power from the heat engine 1002 and electric motor 1002 (through the reduction gearbox 1016) when the clutch 1044 is engaged, and to drive the turbine 1022 and compressor 1024 independently from the heat engine 1002 and electric motor 1006 when the clutch 1044 is disengaged. The lower broken line in FIG. 12 schematically indicates that the positions of the motor 1034 and the compressor 1024 can be switched on the shaft 1020.

Referring now to FIG. 13, a system 1100 is shown wherein the heat engine shaft 1104 and the electric motor shaft 1108 are connected for common rotation. A combining gearbox 1112 connects to a common output shaft 1105 of the electric motor 1106 and the heat engine 1102, and to a shaft 1114 of a turbine 1122 to combine rotational input power from the heat engine 1102, electric motor 1106, and turbine 1122 for providing rotational output power to an output shaft 1114. A reduction gearbox 1116 is connected to the output shaft 1114, wherein a compressor 1124 is connected to be driven on the output shaft 1114. An electrical system 1136 includes a storage 1138 connected through an inverter/rectifier component 1140 to supply power to the motor 1106, or to recover power from the motor 1106 in a generator mode to store in the storage 1138. The other arrangements described above that do not specifically show an electrical system can include a system similar to electrical system 1136, and FIG. 14 includes a similar system 1136 even though the details are not repeated. The compressor 1124 can also be connected to the reduction gearbox 1116 on its own shaft concentric with the shaft 1114, much as described below with respect to FIG. 14. The broken lines in FIG. 13 indicate that optionally the turbine 1122 can be mechanically decoupled from the CGB to drive a generator 1134, which can be connected through an inverter/rectifier component 1142 to charge the storage 1138, which can similarly be applied to other arrangements disclosed herein with the turbine decoupled from the compressor. As indicated by broken lines in FIG. 13, the compressor and a gear box 1118 can be connected to the heat engine 1102 in lieu of connecting the compressor 1124 on the output shaft 1114.

With reference now to FIG. 14, a system 1200 is shown wherein the heat engine shaft 1204 and the electric motor shaft 1208 are connected for common rotation. A reduction gearbox 1216 connected to a common output shaft 1214 of the electric motor 1206 and the heat engine 1202. A turbine gearbox 1218 is connected between the heat engine shaft 1204 and a shaft 1220 of a turbine 1222 so the turbine can rotate at a different rotational speed from the heat engine 1202 and electric motor 1206. A compressor 1224 is connected to the reduction gearbox 1216 through a compressor shaft 1246 concentric with the common output shaft 1214 so the compressor can be driven at a different speed from the common output shaft 1214.

Referring now to FIG. 15, a system 1300 includes a heat engine shaft 1304 and the electric motor shaft 1308 that are connected for common rotation. A super position gearbox 1316 connects to a common output shaft 1314 of the electric motor 1306 and the heat engine 1302, and to a shaft 1320 for driving a turbine 1322 and compressor 1324 to combine rotational input power from the heat engine 1302 and electric motor 1306 for providing rotational output power to an output shaft 1314 and to drive the turbine 1322 and compressor 1324. The super position gearbox 1316 is configured so the speed ratio between the common output shaft 1314 and the shaft 1320 for driving the turbine 1322 and compressor 1324 can vary, e.g., to adjust the speed of the compressor 1324 for altitude or for ground idle.

The turbine 1322 can optionally be decoupled from the compressor 1324 to drive a generator as described above with reference to FIG. 13. Similarly, the arrangement in FIG. 3 can be modified so the turbine 222 is decoupled from the compressor 224 to drive a generator. The heat engine, e.g., heat engine 202 in FIG. 2, can be split and connected on opposite sides of the respective gear box, e.g., the combined gearbox 212 in FIG. 2, as indicated in FIG. 2 with the broken line box 202. This split can be applied to other arrangements above besides the one in FIG. 2. Disconnect clutches or mechanism, e.g., clutch 844 in FIG. 10, can be included, e.g., in each of the shafts 104 and 108 as indicated in FIG. 1 by the broken lines crossing the shafts 104 and 108, for disconnecting the heat engine 102 or electric motor 106 as needed. This can also be applied to other embodiments disclosed above besides the arrangement in FIG. 1.

Even if modules are represented schematically herein vertically on top of each other, those skilled in the art having the benefit of this discourse will readily appreciate that they can be located side by side, one above the other or in any geometrical arrangement and in any order in physical implementations. Similarly, those skilled in the art having had the benefit of this disclosure will readily appreciate that modules represented on one side (right or left) of the respective gearbox herein can also potentially be installed on the other side or even trapped between a respecting reduction gearbox and combining gear box. Module disclosed herein can be installed directly on the respective combining gear box or reduction gear box with a proper speed ratio. Although modules are represented herein with an axial orientation, those skilled in the art having the benefit of this disclosure will readily appreciate that the use of bevel gears (or other mechanical or electrical devices) allows the installation of modules in any suitable orientation. Those skilled in the art having the benefit of this disclosure will readily appreciate that accessories not explicitly represented herein can be included and can potentially be connected mechanically to any module or driven electrically similar to the modules and components disclosed herein. Those skilled in the art having had the benefit of this disclosure will readily appreciate that combining gearboxes and reduction gearboxes disclosed above can be combined into a single respective gearbox.

With reference now to FIG. 16, the hybrid propulsion system 100 includes a heat engine 102 configured to drive a heat engine shaft 104. An electric motor 106 is configured to drive a motor shaft 108. A transmission system 110 includes at least one gear box. The transmission system 110 is configured to receive rotational input power from each of the heat engine shaft 104 and the motor shaft 108 and to convert the rotation input power to output power, as indicated by the circular arrow in FIG. 16.

The at least one gearbox includes a combining gear box 112 connecting to the heat engine shaft 104 and to the motor shaft 108 to combine rotational input power from the heat engine 102 and electric motor 106 for providing rotational output power to an output shaft 114, which can drive a reduction gear box 116 for turning an aircraft propeller, fan, or any other suitable type of air mover for example. A turbine gear box 118 is included, which is connected between the heat engine shaft 104 and a shaft 120 for driving a turbine 122 and a compressor 124 to drive the turbine 122 and compressor 124 at a different rotational speed from the heat engine 102. For example, through the turbine gear box 118, the heat engine 102 can run at 8000 revolutions per minute (RPM) to drive the turbine 122 and compressor 124 at 35,000 RPM. Those skilled in the art will readily appreciate that while described herein using the phrase “to drive the turbine 122 and compressor 124” that the turbine 122 can actually add power to the shaft 120 and therefore cooperates with the heat engine 102 to drive the compressor 124, however, in configurations herein where the turbine 122 and compressor 124 spin at a common speed the compressor 124 and turbine 122 are collectively referred to herein as driven.

The compressor 124 compresses air and supplies the compressed air to the heat engine 102 through the air line 126, which includes heat exchanger 128 for cooling the compressed air. After combustion in the heat engine 102, the combustion products are supplied through a combustion products line 130 to the turbine 122, which extracts power from the compressed combustion products before exhausting them. The configuration shown in FIG. 17 also includes similar connections air lines 126, heat exchangers 128, and combustion products lines 130, and the details for such are not repeated below. The electric motor 106 can be powered to boost horse power, e.g., for take-off, in parallel with the heat motor 102, and can be powered down, e.g., for cruising in level flight, where only the heat motor 102 is needed for power. The compressor 124 and turbine 122 improve the thermal efficiency of the heat engine 102. Similar benefits are derived with the configuration described below with respect to FIG. 17.

The motor shaft 108 includes a disconnect mechanism 144, such as a clutch or the like, to allow the heat engine 102 to rotate with the electric motor 106 stopped. The heat engine shaft 104 includes a disconnect mechanism 146, e.g., a clutch or the like, to allow the electric motor 106 to rotate with the heat engine 102 stopped. The disconnect mechanism 144 of the motor shaft 108 is located between the combining gear box 112 and the electric motor 106, or may be combined into the combining gear box 112. The disconnect mechanism 146 of the heat engine shaft 104 is located between the combining gear box 112 and the heat engine 102, or may be combined into the combining gear box 112. For example, in the event that the electric motor needs to stop rotating, the disconnect mechanism 144 can be disengaged. This mechanically disconnects the electric motor 106 from the transmission system 110, allowing the heat engine 102, compressor 124, and turbine 122 to continue to rotate, which can provide at least some guaranteed power even with the electric motor 106 disabled. Similarly, in the event that the heat engine 102, compressor 124, turbine 122, or turbine gear box need to stop rotating, the disconnect mechanism 146 can disengage to mechanically disconnect the heat engine 102 from the transmission system 110 so that at least some power can still be provided through the electric motor 106.

With reference now to FIG. 17, in the system 300, the heat engine shaft 304 and motor shaft 308 are concentric. A reduction gear box 316 is connected to each of the heat engine shaft 304 and the motor shaft 308, e.g., for driving a propeller with rotational input from the heat engine 302 and electric motor 306. The heat engine shaft 304 connects to a turbine shaft 320 through a turbine gear box 318 for driving a turbine 322 and compressor 324 for driving the turbine shaft 320 at a different speed from the heat engine shaft 304. However, it is also contemplated that optionally the turbine gear box 318 can be omitted by directly connecting the turbine shaft 320 to the heat engine shaft 304 for common rotation or to the reduction gearbox 316 (or to a combining gearbox 112 shown in FIG. 16). Thus the heat motor 302 can drive the turbine 322 and compressor 324 at the same rotational speed as the heat motor 302. Regardless of whether the turbine gear box 318 is included, the heat engine 302 can rotate at a different rotational speed from the electric motor 306.

The disconnect mechanism 344 of the motor shaft 308 is located between the electric motor 306 and the reduction gear box 316. The disconnect mechanism 346 of the heat engine shaft 308 is located between the heat engine 302 and the electric motor 306. Those skilled in the art having the benefit of this disclosure will readily appreciate that the disconnect mechanism 346 can also be located in any suitable location along the shaft 304. Disconnect mechanisms 344 and 346 can be clutches or any other suitable type of disconnect mechanisms. The heat engine shaft 304 runs through the motor shaft 308 and through the disconnect mechanism 344 of the motor shaft 308. The disconnect mechanisms 344 and 346 can disconnect as needed to allow for stoppages of one of the heat engine 302 or electric motor 306 with at least some guaranteed power output to the reduction gearbox 316 of from the working one of the heat engine 302 or electric motor 306 much as described above with respect to FIG. 16.

It is also contemplated that the heat engine shaft 304 and the motor shaft 308 can be combined as a single common shaft, e.g., by mounting the rotor of the electric motor 306 to the heat engine shaft 304, which is connected to the reduction gearbox 316. The electric motor could be independently disconnected by a clutch 347 between the rotor 349 and the heat engine shaft 304, as indicated by broken lines in FIG. 17.

The clutches and disconnect mechanisms disclosed herein can be configured for repeated, at will connection and disconnection. It is also contemplated that the clutches and disconnect mechanisms disclosed herein can be configured for one disconnect only. Those skilled in the art will readily appreciate that while disconnect mechanism are described above for systems 100 and 300, the disconnect mechanisms disclosed herein can readily be applied to any of the systems disclosed herein without departing from the scope of this disclosure.

The methods and systems of the present disclosure, as described above and shown in the drawings, provide for propulsion systems with superior properties including use of hybrid heat engine and electric motor power. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure. 

What is claimed is:
 1. A hybrid propulsion system comprising: a heat engine configured to drive a heat engine shaft; an electric motor configured to drive a motor shaft; and a transmission system including at least one gear box, wherein the transmission system is configured to receive rotational input power from each of the heat engine shaft and the motor shaft and to convert the rotation input power to output power, wherein the heat engine shaft includes a disconnect mechanism to allow the electric motor to rotate with the heat engine stopped.
 2. The system as recited in claim 1, wherein the at least one gearbox includes: a combining gear box connecting to the heat engine shaft and to the motor shaft to combine rotational input power from the heat engine and electric motor for providing rotational output power to an output shaft; and a turbine gear box, wherein the turbine gear box is connected between the heat engine shaft and a shaft for driving a turbine and a compressor to drive the turbine and compressor at a different rotational speed from the heat engine.
 3. The system as recited in claim 1, wherein the heat engine shaft and motor shaft are concentric, wherein the at least one gear box includes a reduction gear box connected to each of the heat engine shaft and the motor shaft, and wherein the heat engine shaft connects to a turbine shaft for driving a turbine and compressor.
 4. The system as recited in claim 3, wherein the heat engine shaft runs through the motor shaft and through the disconnect mechanism of the motor shaft.
 5. A hybrid propulsion system comprising: a heat engine configured to drive a heat engine shaft; an electric motor configured to drive a motor shaft; and a transmission system including at least one gear box, wherein the transmission system is configured to receive rotational input power from each of the heat engine shaft and the motor shaft and to convert the rotation input power to output power, wherein the motor shaft includes a disconnect mechanism to allow the heat engine to rotate with the electric motor stopped.
 6. The system as recited in claim 5, wherein the at least one gearbox includes: a combining gear box connecting to the heat engine shaft and to the motor shaft to combine rotational input power from the heat engine and electric motor for providing rotational output power to an output shaft; and a turbine gear box, wherein the turbine gear box is connected between the heat engine shaft and a shaft for driving a turbine and a compressor to drive the turbine and compressor at a different rotational speed from the heat engine.
 7. The system as recited in claim 5, wherein the heat engine shaft and motor shaft are concentric, wherein the at least one gear box includes a reduction gear box connected to each of the heat engine shaft and the motor shaft, and wherein the heat engine shaft connects to a turbine shaft for driving a turbine and compressor, wherein the disconnect mechanism of the motor shaft is located between the electric motor and the reduction gear box.
 8. The system as recited in claim 7, wherein the heat engine shaft runs through the motor shaft and through the disconnect mechanism of the motor shaft.
 9. A hybrid propulsion system comprising: a heat engine configured to drive a heat engine shaft; an electric motor configured to drive a motor shaft; and a transmission system including at least one gear box, wherein the transmission system is configured to receive rotational input power from each of the heat engine shaft and the motor shaft and to convert the rotation input power to output power, wherein the motor shaft includes a disconnect mechanism to allow the heat engine to rotate with the electric motor stopped, wherein the heat engine shaft includes a disconnect mechanism to allow the electric motor to rotate with the heat engine stopped.
 10. The system as recited in claim 9, wherein the at least one gearbox includes: a combining gear box connecting to the heat engine shaft and to the motor shaft to combine rotational input power from the heat engine and electric motor for providing rotational output power to an output shaft; and a turbine gear box, wherein the turbine gear box is connected between the heat engine shaft and a shaft for driving a turbine and a compressor to drive the turbine and compressor at a different rotational speed from the heat engine, wherein the disconnect mechanism of the motor shaft is located between the combining gear box and the electric motor, and wherein the disconnect mechanism of the heat engine shaft is located between the combining gear box and the heat engine.
 11. The system as recited in claim 9, wherein the heat engine shaft and motor shaft are concentric, wherein the at least one gear box includes a reduction gear box connected to each of the heat engine shaft and the motor shaft, and wherein the heat engine shaft connects to a turbine shaft for driving a turbine and compressor, wherein the disconnect mechanism of the motor shaft is located between the electric motor and the reduction gear box.
 12. The system as recited in claim 11, wherein the heat engine shaft runs through the motor shaft and through the disconnect mechanism of the motor shaft.
 13. The system as recited in claim 9, wherein the heat engine shaft and the motor shaft are combined as a single common shaft connected to the transmission system. 